A number of fasteners have been used in the past for securing one object on another object, as for example, securing an article such as for example a plastic sheet on a metal or other rigid plastic sheet. However, the fasteners of the type, which are improved by the advances of the present invention, and being used presently, have a rather low ratio of insertion force to removal force. In other words, they require considerable force to be inserted into a slot in order to provide adequate removal resistance in order to be removed from the slot. This is ergonomically inferior performance, and the operators may suffer miscellaneous ailments, while productivity is also considerably undermined. In addition the fasteners of the present state in the art suffer from rather inferior Lever/Angle Pulling force.
Lever/Angle pulling force is defined as the force required to separate one part from another part connected with a fastener by pulling said parts apart, not straight away form each other, but sideways from each other, as will be described in more detail hereinbelow.
One of the major objectives of the present invention is to provide fasteners of considerably higher Lever/Angle pulling force than the fasteners of the present state in the art.
Recently, a fastener has been disclosed in U.S. Pat. No. 6,718,599 B2, which is incorporated herein by reference, characterized by ergonomically balanced removal to insertion force ratio. However, even in this case, the Lever/Angle pulling force is relatively low.
Examples of other state in the art fasteners are disclosed in U.S. Pat. No. 6,381,811 (Smith et al.), U.S. Pat. No. 6,353,981, U.S. Pat. No. 6,074,150 (Shinozaki et al.), U.S. Pat. No. 5,987,714 (Smith); U.S. Pat. No. 5,887,319 (Smith); U.S. Pat. No. 5,542,158 (Gronau et al.); U.S. Pat. No. 5,422,789 (Fisher et al.), U.S. Pat. No. 5,373,611 (Murata); U.S. Pat. No. 5,314,280 (Gagliardi); U.S. Pat. No. 5,095,592 (Doerfling); U.S. Pat. No. 4,701,984 (Wyckoff), U.S. Pat. No. 4,792,475 (Bien); U.S. Pat. No. 4,683,622 (Ohelke); U.S. Pat. No. 4,609,170 (Schnabl); U.S. Pat. No. 4,245,652 (Kelly et al.); U.S. Pat. No. 3,864,789 (Leitner); U.S. Pat. No. 3,673,643 (Kindell); U.S. Pat. No. 3,525,129 (Holton); U.S. Pat. No. 2,825,948 (Parkin); U.S. Pat. No. 2,607,971 (Bedford, Jr.); U.S. Pat. No. 2,542,883 (Tinnerman); U.S. Pat. No. 2,329,688 (Bedford, Jr.); U.S. Pat. No. 2,322,656 (Murphy), among others.
U.S. Pat. No. 5,919,019 (Fisher) provides fasteners which can only be permanently installed into a slot; they can only be inserted but not extracted without damage to parts of the fastener. The major engagement is performed by spring strips, while frictional portions of the fastener pass through the slot with at most slight compression, and immediately after the insertion of the fastener they are located in slightly spaced or barely contacting relation with the edges of the slot. They are only activated for engagement after the insertion of a bolt into a hole at the base plate. Thus, the profound effect of the increased removal to insertion ratio (explained in detail hereinbelow) is not recognized, mentioned, or implied. Thus, the intentionally provided distance of the frictional portions away from the edges of the slot by Fisher, during insertion and before use of the bolt, teaches actually away from the instant invention, which recognizes and takes full advantage of the increased removal to insertion ratio by an engagement region having a hindrance portion. As a matter of fact, if the engagement surfaces of the instant invention were located in slightly spaced or barely contacting relation with the edges of the slot, no engagement at all would take place upon insertion of the fastener of this invention into the slot.
U.S. Pat. No. 6,141,837 (Wisniewski) describes a spring fastener comprising bulbous and outwardly projecting portions, which assist in preventing withdrawal of the clip and associated molding from an aperture of a vehicle frame. However, “bulbous projections” are necessarily voluminous, take most of the space between the “reverse bents”, and unless they are manufactured within tight tolerances with regard to the thickness of the frame, the “base plates” do not sit on the frame (see also the Figures), rendering the structure unstable.
U.S. Pat. No. 6,203,240 B1 (Hironaka et al.), U.S. Pat. No. 5,129,768 (Hoyle et al.), U.S. Pat. No. 5,092,550 (Bettini), U.S. Pat. No. 4,981,310 (Belissaire), U.S. Pat. No. 4,712,341 (Harris, Jr. et al.), U.S. Pat No. 4,595,325 (Moran et al.), U.S. Pat. No. 4,431,355 (Junemann), U.S. Pat. No. 4,133,246 (Small), and U. S. Pat. No. 2,424,757 (F. Klump, Jr.) are directed to plastic or metal fasteners which are designed to be just inserted into the slot of a panel, but not extracted without damage to the fastener (if such extraction would be attempted from the front side; the side from which the fastener is inserted into the panel, since the back part of the panel is not reachable in the cases, wherein such types of fasteners are used).
None of the above disclosures of the present state in the art provide satisfactory Lever/Angle pulling force.